A disclaimer! I am not specialized in any form of radiation knowledge. In fact, I am probably the least trustworthy person on this topic. I get most of my radiation knowledge from YouTube and this xkcd comic. As much as I find this interesting, you should not take what I say as fact. I will still try to be as accurate as possible, but I can’t promise anything. If you find any errors feel free to email me. Thanks!

Radiation is such a fascinating topic for me. We can’t feel it, but it’s all around us. If it wasn’t for earth’s magnetic shield, and the kilometres of air above us being irradiated, we would, quite literally, be cooked. The earth’s magnetic shield does the bulk of the work, but the atmosphere is still doing its part. With this in mind, if you were to, say, move yourself closer to space, you should be exposed to more radiation, right? I brought a Geiger counter to find out for myself.

The experiment

I first took a base reading on the ground, at the airport.


Base reading, 20cpm, 0.13uSv/h

@GQ, I had to put tape on my screen because the plastic started to rip apart. If it wasn't for my love of Geiger counters you would be in big trouble mister.


I should start off this post with two notes:

  1. This is what you would call a “hobby counter.” It’s not very precise, but it will suffice for the expreriment.

  2. Our bodies can handle radiation very well. As you’ll see later, the Geiger counter will get quite high, but it’s no reason to panic when you’re on your next flight. Just remember, each ‘count’ affects about one atom in the Geiger counter. Don’t be scared, but be safe. Here’s a better safety chart, measured in mSv (1000x more than 1 uSv.)

With that, and a base reading of 20cpm / 0.13uSv/h out of the way, time to get in the sky!


First reading during ascent. Altitude of 21,793 feet, 85cpm, 0.55uSv/h, maximum read CPM is 89. Text edited in to say "My flight (a surprise)"

Yes, the altitude measurement will be in feet, it's what ATC designates in the sky, it just makes more sense. Metric lovers, I'm here for you. (6643m)


The first measurement I took during the ascent was 85cpm / 0.55uSv/h @ 21,793 ft. This was the highest I had seen my Geiger counter ever go before, and it’s also when the LED adjacent to the screen started blinking red at me. (If you’re curious, the highest I had before was 50cpm measuring a smoke alarm. Try it youself!) If you had this level of ground radiation, you should probably check around to see what’s going on, because something is not right. Maybe it’s your Geiger counter.


Second reading during ascent. Altitude of 28,035 feet, 153cpm, 0.99uSv/h, maximum read CPM is 158.

That escalated quickly.


The second measurement I took during ascent was 153cpm / 0.99uSv/h @ 28,035 ft, and that’s because this is when my Geiger counter finally hit 1 uSv/h!! 🎉

One micro-Sievert is about the same radiation you would receive from an arm x-ray. (Try to guess my source, impossible edition.) Anyways, we’re on a plane so it’s only up from here.


Third reading during ascent. Altitude of 29,909 feet, 201cpm, 1.31uSv/h, maximum read CPM is 201.

I can't think of a funny joke for this one, which means Davi.LOL is SELLING AD SPACE! For just one LOW price, YOU can have your joke seen here around THE WORLD! Supply is limited! Act now!


Coincidentally, 200cpm and 30,000 ft of altitude converged at the same time! My third reading during ascent was 201cpm / 1.31uSv/h @ 29,909 ft.


A headphone jack plugged into the Geiger counter

This is also around the time when I noticed I could plug my headphones into my Geiger counter. Ah, the sweet sound of music. Click, click click, click, click click click.


Cruising altitude reading. Altitude of 36,999 feet, 297cpm, 1.93 uSv/h, maximum read CPM is 355.

We've hit our cruising altitude.


The plane, and the Geiger counter, seem to have stablized. My final reading is 297cpm / 1.93 uSv/h @ 36,999 ft. It’s funny how all of the results seem to have stablized around round numbers! If you’re ever in a conversation about this (which, if you are, awesome!! Invite me!) You can safely recall the values of 300cpm, 2 uSv/h, and 37,000 ft. Well, I guess that settles it, then.


A reading in between Nunavut, Canada, and Greenland. No altitude reading, 460cpm, 2.99uSv/h, maxmimum read is 460cpm.

Uh oh.


It seems the second factor, earth’s magnetic shield, is coming into play!!

If you’ve ever seen a diagram of earth’s magnetic shield before, you’ll know it’s weaker at the poles. This was the furthest north that the flight went, in between Nunvavut and Greenland. At this point on earth, combining a lack of atmosphere and weak magnetic shield, my Geiger counter reads 460cpm / 2.99 uSv/h. I didn’t check our altitude, but I imagine it was still 37,000 feet.

This is around the time my Geiger counter started estimating its reading. If there was too much radiation, it would make a shorter, faster approximation of the current levels. It will go 1, 3, 10, 50, 460 in about 3 seconds, and then slow down and find a precise reading from there. I think it stablized around 400cpm.

That marks the end of my experiment! My Geiger counter was fed well.

Conclusion

Line graph of datapoints. Altitude on the horizontal, cpm and uSv/h on the vertical.

Note here that the altitude is on the horizontal axis.

Altitude (ft) Radiation exposure (µSv/h) Counts (cpm)
3000 0.13 20
21793 0.55 85
28035 0.99 153
29909 1.31 201
36999 1.93 297

If you want to replicate this experiment for yourself, here are some suggestions:

  1. Turn off the speaker and the alarm on your Geiger counter! If you don’t, everyone is going to be looking at you. If you want to listen, plug your headphones into the side like I did.

  2. Tell me about your experiment! I would love to hear that my blog post inspired someone to do something awesome. You can find my email at the bottom.

Thanks for reading! I’ll be making some new blogposts soon revealing where I’ve ended up after the flight.

Join me next time when I get deported for trying to X-ray my Geiger counter through airport security!